Chaser



Nov. 14,1933. 5. F. NEWMAN ET AL 1,935,297

CHASER Filed Dec. 16, 1950 s Sheets-Sheet 1 gwuwntow I; SamudF Newman elmrluAifilmdc/zi ldrz Nov. 14,1933. s. F. NEWMAN ET AL CHASER 3 Sheets-Sheet 3 Filed Dec. 16, 1930 gwuentou Z szlmuelFjl/fwmdfl liar/edfljfelmdc/u'ddel Patented Nov. 14, 1933 CHASER Samuel F. Newman and Charles A. Reimschissel, Waynesboro, Pa., assignors to Landis Machine Company, Waynesboro, Pa., a corporation of Pennsylvania Application December 16, 1930 Serial No. 502,799

4 Claims.

This invention relates to thread cutting chasers or cutters which go to make up a set in a threading die and to the method of'forming such chasers and cutters. v

An object of the invention is to provide a set of thread cutting elements which will correctly form the tops and bottoms of the screw threads and particularly produce smooth out flanks on the screw threads.

A further object of the invention is to provide a set of thread cutting chasers in which the coolant may penetrate to the parts of the cutters most affected by the heat and thus better exercise its cooling effect on the die during operation.

Further objects and advantages will become apparent as the description proceeds.

In a thread cutting die head there are a number of thread cutting chasers or cutters from three to twenty-four which go to make up a complete set of chasers, the chasers, of course, are machined, with the pitch of the thread properly positioned on the chaser. For example, in a die head having four chasers forming a set each chaser will have the thread form positioned one fourth of the pitch of the thread from the chaser immediately preceding it in the set, in case of ten chasers one tenth, etc. This invention deals with the form of the several chasers of the set which form a die head.

Referring to the accompanying drawings which are made a part hereof and on which similar reference characters indicate similar parts,

Figure 1 is a front view of a tangential chaser showing the thread cutting serrations,

Figure 2 is an end view of theodd numbered chasers in a set forming a die head,

Figure 3, an end view of the even numbered chasers in a set,

Figure 4, a view of the odd numbered chasers showing the serrations thereon in relation to the threaded work,

Fig. 5, an enlarged sectional view of a portion of the parts shown in Figure 4,

Figure 6, a view similar to Figure 4 of the even numbered chasers of a set,

Figure '7, an enlarged view similar to Figure 5 chasers forming a set in a die.

fore it has been the practice to form the thread grooves on the cutters or chasers in exact duplication of the thread standard to be produced on the work. Likewise in the art of producing tapered threads on pipe, tubes and the like it has heretofore been the practice to form the thread cutting grooves on the cutters or chasers as an exact duplication of the thread standard to be produced or to form every other chaser or cutter so that every other thread groove will be formed by a chaser, this latter method being known as drop tooth, skip tooth or interrupted thread.

In the invention set forth in this application every other thread cutting chaser forms one side of the thread to be cut and the alternate chasers form the other side of the thread to be cut. This arrangement insures that the thread cutting chaser will cut a smooth surface on the side of the thread being formed since it permits the coolant to penetrate to the serrations performing the cutting and permits the material which is cut from one flank of thread form to escape freely as there is no interference from any chip from opposite flank such as is true when thread is formed by means of cutters having the same form as on the work. When the cutters have the same form as the work the chips block each other and tear the threads.

The chasers and the work in the attached drawings are shown fragmentary and somewhat diagrammatically, only such parts' being shown as will illustrate the invention.

In the drawings numeral 10 indicates a portion of the work being threaded and 11 and 12 indicate respectively odd numbered and even numbered The chasers have thread cutting serrations l3 and 14 for cutting threads in the work. Of the thread cutting serrations 13, the edge 15 is formed to cut accurately the corresponding side 16 on the work but the side 1'7 of the serrations on the chaser is cut away so as to leave a space 18 between the edge 1'7 and the edge 19 of the work. After the chaser has made its cut, therefore, one side of the threaded groove in the work will have been cut to finished form by one side of the serrations on the chasers. The space 18 between the other side of the thread cutting serrations and the side of the work forms a clearance through which lubricating oil or coolant may pass intoclose contact with the chaser to carry off the heat generated during the cutting of the thread.

Following in alternate relation are the even numbered chasers 12 in which the side 20 of the threading serrations 14 will cut the work to finish the threaded side at 21. In this group of chasers the side 22 is cut back to leave a clearance 23 between the edge of the chaser and the edge 16 on the work which edge 16 was out to its finished shape by the odd numbered chasers 11 of the set. Clearance 23, as mentioned before provides a channel through which a coolant may penetrate to the tips of the cutting serrations to cool them and thus maintain them in the best of condition for performing their work.

The clearances 18 and 23 likewise permit chips to escape without jamming or distorting the tips of the thread on the work, as the chip is cut on alternating sides of even and odd numbered chasers.

What has been said about the serrations in their full size is likewise true of the truncated serrations at the throat of the chasers, as for example, in the chaser shown in Figure 4. the sides 24 of the serrations on the chasers at the throat are cut back so that a clearance is left at 25 between the edge of the chaser and the finished surface of the work. The corresponding even numbered chasers 12 have the edges 26 of the serrations of the chaser at its throat cut back to leave a clearance at 2'7 and in this form the edge 28 of the serration in the throat oi the chaser cuts the corresponding edge 29 on the side of the thread in the work. In action therefore the cutting portions of the chasers are provided with a clearance through which a coolant may penetrate to the portion of the chaser which is most heated. Flat surfaces 37 are formed at the bottom of the grooves in the chaser whereby basic flats 38 are formed at the top oi? the threads on the work and flat surfaces 39 are formed at the top of the serrations on the chaser whereby basic flats 40 are formed at the bottom of the threads on the work as or if desired. It should be noted in our invention that the serrations excepting those at the throat on all chasers cut threads to the full depth.

In operation these cutting edges therefore are maintained in a cool condition and therefore kept in the best of condition for operating on the work. Likewise any portions of themetal which is sheared .from the work may find ready means of escaping with less injury to the threads than is true of chasers heretofore known.

In Figures 2 and 3 the chasers are shown as of the tangential type having the beveled edge or base 30 adjacent to the threaded serrations 13 and a portion oi its back cut away at 31 to provide a groove 32 parallel to the beveled base or edge by means of which groove the chaser is secured in position in a die head. While tangential chasers of the type just described have proved to be highly efficient for carrying out the particular invention described in this application the invention is not limited to this type of chaser. It may be applied equally well with chasers in which there is a mutilated screw-thread formed at the junction of the beveled base and the back, the screw threads serving to adjust the chaser axially in a die head such for example as chasers shown in the patents to Fisher 1,075,203, October 7, 1913; 1,134,983, March 30, 1915, and to New man, 1,739,646, December 17, 1929.

The invention is likewise applicable to tangen= tial chasers having a beveled base or edge adjacent to thread cutting serrations, a portion of its back cut away forming a beveled ridge or edge, such for example as the chasers shown ill merger the patent to Shearer 1,738,847, December 19, 1929.

The invention moreover is not limited to tangential chasers but is adapted for use equally well with hobbed or milled chasers such for ex ample as those shown diagrammatically in Figure 9.

In all the forms of chasers to which the invention is applied the thread cutting serrations on the chasers are kept cooler during cutting ac= tion than is possible with other forms of chasers and the chips cut from the work have less opportunity for jamming and therefore injury to the sides or the tops of the threads on the work. Better work therefore is insured by chasers of this type as well as the chasers are insured a longer life than is true of other forms of chasers.

Figure 8 shows diagrammatically a set of tan gential chasers ll positioned in a die head with their cutting edges in engagement with the work 33.

In Figure 9 is shown a set of hobbed or milled chasers 3d positioned in cutting relation to the work 35.

It will be obvious to those skilled in the art that various changes may be made in our device without departing from the spirit of the inven= tion and therefore we do not limit ourselves to what is shown in the drawings and described in the specification, but only as indicated by the appended claims.

Having thus fully described our said invention, what we claim as new and desire to secure by letters Patent, is:

1. A thread cutting die for cutting tapered screw threads, comprising a set oi threag chasers, every other chaser in said set having thread cutting serrations for can one side only of the threads, the remaining chasers hav= ing serrations for forming the other side of the threads, the angle formed by the sides of the thread cutting serrations being less than the angle oi the finished threads desired to be out, the bottoms of the grooves between said sides on all of said chasers being wider than the width or the tops of the screw threads cut on the work, the root and the side angles oi the serrations be= ing the same for the full width of the chasers sub stantially as set forth.

2. In a die head for cutting tapered screwthreads on tubular work, a set of three, chasers, the alternate chasers of which cut alter nate sides oi the threaded groove, the sides of ad= jacent thread cutting serrations terminating in flat surfaces all oi which lie in a single plane, the planes of the inactive faces of the thread cut ting serrations lying at a greater angle with re= spect to the axis of the work to be threaded than the planes oi the active surfaces of the thread cutting serrations, the root and the side angles angle operating to cut one side of the thread groove to its full depth, the even nbered chasers in the set having serrations, the sides of which also he at witilelelnt angles with respect to the axis of the pipe being threaded and the sides which lie at the lesser angle operat to Mill) till its

cut the remaining sides of the thread groove to' their full depth, the root and side angles of the serrations on any chaser being the same for the full width of the chaser substantially as set forth.

4. In a die for cutting screw tapered threads on tubular work, a set of tangential chasers consisting of twogroups of chasers having thread cutting serrations on their faces, each of the chasers having a beveled base adapted to seat in a chaser holder and having a portion of its back cut-away to receive a holding clamp, all the cutting serrations of one group of chasers being formed alike, said cutting serrations having one side at a greater angle to the axis of the pipe being threaded than the other side of the same serrations, the cutting serrations of the other group of chasers being all alike but diiferent from those in the first group in that the side lying at the greater angle and the side lying at the lesser angle are reversed from those of the first group, the side lying at the lesser angle of each serration operating to out the side of the thread groove to its full depth, the root and side angles of the thread forming serrations being the same for the full width of the chaser substantially as set forth.

SAMUEL F. NEWMAN.

CHARLES A. REIMSCHISSEL. 

